assume cs:code
code segment
start: mov ax,cs
       mov ds,ax
       mov si,offset s1
       mov ax,0
       mov es,ax
       mov di,200h
       mov cx,offset s2-offset s1
       cld
       rep movsb

       mov ax,0
       mov es,ax
       mov word ptr es:[7ch*4],200h
       mov word ptr es:[7ch*4+2],0

       mov ax,4c00h
       int 21h

   s1: push bp
       mov bp,sp
       dec cx
       jcxz s3
       add [bp+2],bx
   s3: pop bp
       iret
   s2: nop

code ends
end start
